CN112689227B - Piezoelectric MEMS loudspeaker imitating cochlea spiral vibrating membrane and preparation method - Google Patents
Piezoelectric MEMS loudspeaker imitating cochlea spiral vibrating membrane and preparation method Download PDFInfo
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Abstract
本发明提供一种仿耳蜗螺旋形振动膜结构的压电MEMS扬声器及其制备方法，包括：基底，基底的底部设有背部腔，背部腔的腔室呈仿耳蜗螺旋形；第一电极设置于基底的上表面，且第一电极与背部腔的腔室间隔致动层；压电层设置于第一电极的上表面；第二电极设置于压电层上；由致动层、第一电极、压电层及第二电极构成仿耳蜗螺旋形振动膜，且仿耳蜗螺旋形振动膜与背部腔的位置上下对应且形状相匹配。本发明实现了在一个仿耳蜗螺旋形腔室结构上，有多个共振频率覆盖在20Hz‑20000Hz之间的高声压级压电MEMS扬声器；仿耳蜗螺旋形振动膜完全覆盖了人耳能够听到的音频范围，能达到足够满足商业应用的声压级，可用于手机扬声器，耳机，助听器等可穿戴电子设备。
The invention provides a piezoelectric MEMS speaker with a cochlear helical vibrating membrane structure and a preparation method thereof. the upper surface of the substrate, and the first electrode and the cavity of the back cavity are spaced from the actuation layer; the piezoelectric layer is arranged on the upper surface of the first electrode; the second electrode is arranged on the piezoelectric layer; the actuation layer, the first electrode , the piezoelectric layer and the second electrode form a cochlear-like spiral vibrating membrane, and the cochlear-like spiral vibrating membrane and the back cavity correspond up and down in position and match in shape. The invention realizes that on a cochlear-like spiral chamber structure, there are a plurality of high-sound-pressure-level piezoelectric MEMS speakers whose resonant frequency covers between 20Hz-20000Hz; It can reach the sound pressure level sufficient for commercial applications, and can be used in wearable electronic devices such as mobile phone speakers, earphones, and hearing aids.
Description
Technical Field
The invention relates to the field of loudspeakers, in particular to a piezoelectric MEMS loudspeaker simulating a cochlear spiral diaphragm and a preparation method thereof, wherein the loudspeaker completely covers the frequency range of 20Hz-20000Hz which can be heard by human ears.
Background
The speaker is one of the core components of portable electronic products, such as notebook computers, smart phones, earphones, wireless earphones, and human-computer interfaces. With the increasing demand of wearable devices, the development of micro speakers tends to be miniaturized, light-weighted, low-power, and high-sound-pressure. The rapid development of MEMS (Micro-Electro-Mechanical Systems) technology has enabled smaller and lower power devices, with MEMS electrodynamic, capacitive and piezoelectric microspeakers providing alternatives to traditional loudspeakers.
Among them, the electrodynamic MEMS micro-speaker realizes electro-acoustic conversion according to the motor principle, and the electrodynamic MEMS micro-speaker is the most common type of the existing speaker because of better acoustic performance. However, the electrodynamic MEMS speaker has disadvantages of large current, complicated packaging process, and the like due to the requirement for the magnet. Although the conventional electrodynamic micro-speaker has low power consumption, large variation in manufacturing process, and moderate sound quality, it is still not replaced by the MEMS micro-speaker, mainly because the chip size is relatively large and cannot generate sufficient sound pressure level. The electrostatic MEMS speaker drives a diaphragm and pushes air using two independent electrodes that generate electrostatic force. Although the capacitive MEMS micro-speaker is the leading speaker product occupying the market, and because the electrostatic speaker has the advantages of extremely light diaphragm mass and excellent resolving power, it can fully express the musical spirit, but its diaphragm displacement and sound pressure level are limited by the gap, and there are more application limitations of the pull-in effect and high driving voltage. The piezoelectric MEMS micro-speaker realizes sound pressure output based on the piezoelectric effect of the piezoelectric film material, and has the advantages of simple manufacture, high signal-to-noise ratio, high response speed, dust prevention and the like compared with a capacitive MEMS micro-speaker. To date, piezoelectric speakers have been developed with various piezoelectric materials, such as ZnO, AlN, PZT, PMN-PT, PZN-PT, etc. PZT piezoelectric materials are the most widely used piezoelectric materials because of their high piezoelectric charge constants and electromechanical coupling coefficients. However, piezoelectric MEMS speakers face the problem of relatively low sound pressure levels.
Through the search discovery for the prior art:
haoran Wang, Zhenfang Chen et al in Sensors and actors A Physical write "A high-SPL piezoelectric MEMS loud speaker based on piezoelectric PZT". A circular closed-film piezoelectric MEMS speaker based on ceramic PZT is reported that can generate a high sound pressure level at a small driving voltage, but the use of an adhesive layer causes uncertainty in the film thickness, and the resonance frequency is 4.2kHz, so that the sound pressure level cannot be guaranteed to be always at a high sound pressure level in the frequency range of 20-20 kHz.
Hsu-Hsiang Cheng, Weiileun Fang et al, at "2020 IEEE 33rd International Conference on Micro Electro Mechanical Systems (MEMS)" Conference, write "Piezoelectric microspaker using novel driving approach and electrode design for frequency range improvement". A dual-electrode driving mode including an edge electrode and a center electrode is introduced, which not only can maintain a sound pressure level at a low frequency in a piston vibration mode by driving a diaphragm by the edge electrode, but also can further increase the sound pressure level at a high frequency by driving of the center electrode. Improved piezoelectric MEMS loudspeaker at 2VppFrom 2.6kHz to 20kHz, 15dB higher than previously designed piezoelectric MEMS speakers. Although the sound pressure level at low frequencies is increased, it is lower at high frequencies, between 10kHz and 20kHz and sometimes only around 52 dB.
Shih-Hsiung Tseng, Weieun Fang et al, at "2020 IEEE 33rd International Conference on Micro Electro Mechanical Systems (MEMS)" Conference, "Sound pressure and Low frequency enhancement using PZT MEMS microspeaker design". A piezoelectric MEMS array microspeaker is disclosed, which comprises four triangular plates, a connecting mass block and dual driving electrodes, wherein the inner and outer electrodes on the triangular plates are driven 180 DEG out of phase. At a driving voltage of only 2VppThe sound pressure levels of this micro-speaker with 5 arrays at 100Hz, 1kHz were 81.4dB and 84.7dB, respectively. However, the structure and the manufacturing process of the array type piezoelectric MEMS speaker are complicated.
Stoppel, c.eisermann et al, at 201719 th International Conference on Solid-State transducers, actors and Microsystems, written "Novel membrane-less two-way MEMS loud speaker low-velocity MEMS on piezoelectric dual-channel Actuators", show a Novel two-channel piezoelectric MEMS speaker based on a concentric cascade PZT driver, achieving a sound pressure level of 95dB at frequencies above 800Hz, with two diaphragm structures corresponding to two different resonance frequencies.
In summary, the following steps: the piezoelectric MEMS speakers reported at present are mostly focused on a piezoelectric MEMS speaker with one resonant frequency, even a piezoelectric MEMS speaker with two resonant frequencies, and also an array type piezoelectric MEMS speaker. With the development of wearable electronic devices, better performance, full coverage frequency, piezoelectric MEMS speakers with higher sound pressure level are becoming a necessary trend.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a piezoelectric MEMS loudspeaker with a cochlear-like spiral diaphragm structure and a preparation method thereof.
The invention provides a piezoelectric MEMS loudspeaker of a simulated cochlea spiral diaphragm structure, which comprises:
the back cavity is arranged at the bottom of the substrate, and a cavity of the back cavity is in a cochlear-like spiral shape;
a first electrode disposed on the upper surface of the substrate and spaced apart from the cavity of the backside cavity by an actuation layer for generating vibrations; when a voltage is applied between the first electrode and the second electrode, the actuation layer vibrates.
A piezoelectric layer disposed on an upper surface of the first electrode;
a second electrode disposed on the piezoelectric layer;
the actuating layer, the first electrode, the piezoelectric layer and the second electrode form a cochlear-like spiral vibrating membrane, and the cochlear-like spiral vibrating membrane corresponds to the back cavity up and down in position and is matched in shape.
Preferably, the outer contour of the back cavity overlaps the outer contour of the cochlear-like spiral diaphragm.
Preferably, the cochlear-like spiral diaphragm is wider from the center along the spiral line to the outer edge.
Preferably, the cochlear helical shaped chamber of the back cavity is wider and wider from the center along a spiral line to the outer edge, and the width of the back cavity is larger than the width of the cochlear helical shaped diaphragm.
Preferably, the first electrode is provided with a first bonding pad, and the first bonding pad is exposed to the upper surface of the device; the second electrode is provided with a second pad.
Preferably, the substrate is an SOI wafer, a flexible material substrate, a metal substrate or a non-metal substrate.
Preferably, the material of the first electrode and the second electrode is any one of platinum Pt, gold Au, chromium Cr or aluminum Al.
Preferably, the piezoelectric layer is made of any one piezoelectric material of PZT piezoelectric ceramics, zinc oxide ZnO, aluminum nitride AlN, lead magnesium niobate-lead titanate PMN-PT or polyvinylidene fluoride PVDF.
Preferably, the spiral turns of the cochlear-like spiral diaphragm and the back cavity are matched with the real cochlear turns.
The second aspect of the invention provides a method for preparing a piezoelectric MEMS loudspeaker with a cochlear-like spiral diaphragm structure, which comprises the following steps:
preparing a first electrode on a substrate;
preparing a piezoelectric layer on the first electrode;
preparing a second electrode on the piezoelectric layer;
etching the second electrode to obtain a cochlear-like spiral second electrode pattern and a second electrode pad;
wet etching is carried out on the piezoelectric layer, a cochlear spiral-shaped piezoelectric layer pattern is etched, and the first electrode pad are exposed;
and etching the back of the substrate to form a cochlear-like spiral back cavity, wherein the part of the substrate, which is not etched, between the cavity of the back cavity and the first electrode is an actuating layer.
The above speaker, the resonant frequency is for but not limited to 1 resonant frequency in the ranges of 20Hz-1000Hz, 1000Hz-10000Hz and 10000Hz-20000Hz, and is also applicable to 2, 3 or more resonant frequencies in each frequency range.
The resonance frequency of the loudspeaker aims at but is not limited to the resonance frequencies with the same number in the ranges of 20Hz-1000Hz, 1000Hz-10000Hz and 10000Hz-20000Hz, and the loudspeaker is also suitable for the resonance frequencies with different numbers in each frequency range.
Compared with the prior art, the invention has at least one of the following beneficial effects:
according to the loudspeaker, the characteristics that the cochlear spiral cavity structure has different resonance frequencies at different sections of different spiral vibration membranes are utilized, so that a plurality of high-sound-pressure-level piezoelectric MEMS loudspeakers with the resonance frequencies covering between 20Hz and 20000Hz are arranged on a cochlear-imitated spiral cavity structure; the cochlear-like spiral diaphragm completely covers the audio frequency range which can be heard by human ears, can reach the sound pressure level which can sufficiently meet commercial application, has compact structure, smaller volume and excellent performance, and can be used for wearable electronic equipment such as mobile phone speakers, earphones, hearing aids and the like.
Drawings
Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:
fig. 1 is a front view of a piezoelectric MEMS speaker of a cochlear-like spiral diaphragm structure in accordance with a preferred embodiment of the present invention;
FIG. 2 is a schematic diagram of the back cavity of a cochlear-like spiral diaphragm structured piezoelectric MEMS speaker according to a preferred embodiment of the present invention;
fig. 3 is another angular cross-sectional view of a cochlear-like spiral diaphragm structure piezoelectric MEMS speaker according to a preferred embodiment of the present invention;
fig. 4 is a cross-sectional view of a piezoelectric MEMS speaker of a cochlear-like spiral diaphragm structure in accordance with a preferred embodiment of the present invention;
fig. 5 is a flow chart of the fabrication of a piezoelectric MEMS speaker with a cochlear-like spiral diaphragm structure according to a preferred embodiment of the present invention;
the scores in the figure are indicated as: a second bonding pad 1, a first bonding pad 2, a second electrode 3, a substrate 4, a dorsal cavity 5 and a cochlear-like spiral chamber 6.
Detailed Description
The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that variations and modifications can be made by persons skilled in the art without departing from the spirit of the invention. All falling within the scope of the present invention.
Referring to fig. 1, a piezoelectric MEMS speaker with a cochlear-like spiral diaphragm structure according to a preferred embodiment of the present invention includes a substrate 4, a first electrode, a piezoelectric layer, a second electrode 3, and an actuation layer;
referring to fig. 2, 3 and 4, the bottom of the base 4 is provided with a dorsal cavity 5, the dorsal cavity 5 having a cochlear-like spiral chamber 6.
A first electrode disposed on the upper surface of the substrate 4 and spaced apart from the chamber of the backside cavity 5 by an actuation layer;
the piezoelectric layer is arranged on the upper surface of the first electrode;
the second electrode 3 is arranged on the piezoelectric layer;
the cochlear simulation spiral vibrating membrane is formed by the actuating layer, the first electrode, the piezoelectric layer and the second electrode 3, and the cochlear simulation spiral vibrating membrane is up-down corresponding to the back cavity 5 and matched in shape. Preferably, the cochlear implant spiral diaphragm corresponds to the cochlear implant spiral chamber 6 of the back chamber 5 in structure and number of spiral turns.
The above speaker, the resonant frequency is for but not limited to 1 resonant frequency in the ranges of 20Hz-1000Hz, 1000Hz-10000Hz and 10000Hz-20000Hz, and is also applicable to 2, 3 or more resonant frequencies in each frequency range. The resonant frequencies are directed to, but not limited to, the same number of resonant frequencies in each of the 20Hz-1000Hz, 1000Hz-10000Hz, and 10000Hz-20000Hz ranges, and are also applicable to different numbers of resonant frequencies in each frequency range.
In other partially preferred embodiments, the outer contour of the dorsal cavity overlays the outer contour of the cochlear-like spiral diaphragm.
In other partially preferred embodiments, and with reference to FIG. 1, the cochlear-like spiral diaphragm is wider from the center along the spiral line to the outer edge. The width variation range of the cochlear-simulated spiral diaphragm is 0-5 mm.
In other partially preferred embodiments, referring to fig. 3, the cochlear helical shaped chamber of the back cavity is wider from the center along the spiral line to the outer edge, and the width of the cochlear helical shaped chamber is slightly larger than the width of the cochlear helical shaped diaphragm. The width of the spiral chamber of the imitated cochlea ranges from 0 mm to 6 mm.
In other partially preferred embodiments, the first electrode is provided with a first pad 2, and the first pad 2 is exposed to the upper surface of the device; the second electrode 3 is provided with a second pad 1, and the second pad 1 may be connected to any portion of the second electrode 3.
In other partially preferred embodiments, the substrate 4 is an SOI wafer, a flexible material substrate, a metal substrate or a non-metal substrate. The flexible material substrate can be selected from PDMS, PE, PI and other flexible material substrates.
In some other preferred embodiments, the material of the first electrode and the second electrode is any one of platinum Pt, gold Au, chromium Cr or aluminum Al.
In other preferred embodiments, the piezoelectric layer is made of any one of PZT piezoelectric ceramics, zinc oxide (ZnO), aluminum nitride (AlN), lead magnesium niobate-lead titanate (PMN-PT), or polyvinylidene fluoride (PVDF).
In other preferred embodiments, the spiral turns of the cochlear-like spiral diaphragm and the back cavity are matched with the real cochlear turns. However, the spiral number of turns of the cochlear-like spiral diaphragm is not limited to 2.5 turns of a real cochlea, and is also applicable to all the turns of 3 turns, 3.5 turns, 4 turns and the like; the spiral number of turns of the cochlear-imitated spiral cavity of the dorsal cavity is not limited to 2.5 turns of a real cochlea, and is also applicable to all the turns of 3 turns, 3.5 turns, 4 turns and the like. In specific implementation, different spiral turns can be selected according to the expansion requirement of frequency.
Based on the structural characteristics of the piezoelectric MEMS speaker with the cochlear-like spiral diaphragm structure, in a specific embodiment, the piezoelectric MEMS speaker with the cochlear-like spiral diaphragm structure can be prepared by the following method, which is performed according to the following steps:
s1, as shown in a (a) of a picture in figure 5, coating photoresist 5 microns on the front surface of the prepared PZT-SOI wafer, pre-baking for 90S, exposing for 45S, developing for 45S, washing with deionized water for 30S, drying with nitrogen, post-baking for 12min, then etching an upper electrode (a second electrode) by ion beams, finishing patterning the upper electrode, and removing the photoresist to obtain a cochlear-like spiral upper electrode; the width of the cochlear-like spiral upper electrode is gradually wider from the center to the outer edge along the spiral line, and the width is gradually increased from 0 to 1 mm; the spiral number of turns of the upper electrode of the cochlear-imitated spiral shape is matched with that of the real cochlea and is 2.5 turns; and a line with the line width of 30 mu m is etched on the upper electrode, and a square second bonding pad 1 connected with the line is etched, wherein the length and the width of the second bonding pad 1 are both 300 mu m.
As a preferred mode, the PZT-SOI wafer is prepared by the following method: selecting an SOI wafer as a substrate; and respectively sputtering a Pt electrode (first electrode), PZT piezoelectric ceramics and a Pt electrode (second electrode) on the SOI wafer in sequence to prepare the PZT-SOI wafer. The thicknesses of the first electrode and the second electrode are both 100 nm; the thickness of the PZT piezoelectric ceramic is 1 μm. Of course, the PZT piezoelectric ceramic (piezoelectric layer) is not limited to being prepared by sputtering, and spin coating or the like may be used.
S2, as shown in (b) of FIG. 5, coating photoresist 5 μm on the upper surface with the upper electrode, prebaking for 90S, exposing for 45S, developing for 45S, rinsing with deionized water for 30S, drying with nitrogen gas, postbaking for 12min, and wet etching the PZT piezoelectric ceramic for 90S. Then immersing PZT piezoelectric ceramics into the prepared etching liquid for etching, and stirring the etching liquid by using a magnetic stirrer to improve the etching uniformity and speed; wherein, the stirring speed is 170r/min during PZT etching, and the stirring temperature is normal temperature during PZT etching; putting the etched PZT-SOI into the prepared HNO3Soaking in the solution for 3 min; finally, the mixture is put into deionized water to be soaked for a few minutes so as to clean and remove surface impurities. Drying by nitrogen and vacuum drying. And wet etching the exposed square first bonding pad to expose the first bonding pad on the upper surface of the device, wherein the length and the width of the first bonding pad are both 300 mu m.
As one excellenceIn a selected mode, the etching solution for wet etching of the PZT piezoelectric ceramics can be prepared by the following method: first 1.40g NH4F, slowly adding the mixture into 2ml of deionized water, and continuously stirring until the mixture is completely dissolved; then 1ml NH4Slowly pouring F (40%) into 5ml of HF solution, and continuously stirring to uniformly mix the F and the HF solution to form BHF solution; then 1ml BHF, 30ml HCl and 190ml H2Preparing etching mixed liquid from the O, and fully stirring to fully and uniformly mix the etching mixed liquid to obtain etching liquid; and then immersing the PZT piezoelectric ceramics into etching liquid for etching, and stirring the etching liquid by using a magnetic stirrer to improve the etching uniformity and speed.
The above-mentioned required HNO3The solution was prepared as follows: adding 9ml of HNO3Put into 16ml of H2And O forms a solution and is stirred uniformly.
In S2, the method for etching PZT piezoelectric ceramics is not limited to wet etching, but may also be applied to various dry etching techniques such as ion beam etching.
S3, as shown in (c) of FIG. 5, coating 5 μm photoresist protection on the front side of the PZT-SOI wafer, coating 20 μm photoresist on the back side, prebaking for 2min, developing for 130S, rinsing with deionized water for 30S, drying with nitrogen, prebaking for 12min, and etching with NMC medium to obtain 1.5 μm SiO2(ii) a Etching to obtain the SiO with the spiral shape of the imitated cochlea2A graph; and imitates the SiO of the spiral shape of the cochlea2The width of the graph is gradually wider from the center to the outer edge along the spiral line, and is 0.2mm larger than that of the cochlear-like spiral upper electrode, so that the back cavity can cover the whole front cochlear-like spiral vibrating membrane; cochlear spiral-shaped SiO2The spiral number of turns of the graph is matched with that of the real cochlea, and the number of turns of the spiral is 2.5.
S4, as shown in FIG. 5 (d), then deep silicon etching Si to SiO with NMC2Stop barrier layer of SiO2The barrier layer is arranged between the lower electrode and the back cavity and is used as an actuating layer to form a back cavity with a cochlear-like spiral cavity structure, and the preparation of the back cavity is completed.
In S3 and S4, the above-mentioned Si and SiO are added2The etching method is not limited to dry etching, and can also be applied to wet etching and other technologies.
Based on the structural characteristics of the piezoelectric MEMS speaker with the cochlear-like spiral diaphragm structure, in another specific embodiment, the piezoelectric MEMS speaker with the cochlear-like spiral diaphragm structure can be prepared by the following steps:
s10, as shown in (a) of FIG. 5, coating photoresist 5 microns on the front surface of the prepared PZT-SOI wafer, pre-baking for 90S, exposing for 45S, developing for 50S, washing with deionized water for 30S, drying with nitrogen, post-baking for 12min, then etching the upper electrode for 12min by ion beams, finishing patterning the upper electrode, and removing the photoresist to obtain a cochlear-like spiral upper electrode; the width of the upper electrode of the cochlear-like spiral shape is gradually wider from the center to the outer edge along the spiral line, and the width is gradually increased from 0 to 1.2 mm; the spiral number of turns of the upper electrode of the cochlear-imitated spiral shape is matched with that of the real cochlea, and the number of turns of the spiral is 3; and a line with the line width of 35 mu m is etched on the upper electrode, and a square second bonding pad connected with the line is etched, wherein the length and the width of the second bonding pad are both 260 mu m.
As a preferred mode, the PZT-SOI wafer is prepared by the following method: selecting an SOI wafer as a substrate; and respectively sputtering a Pt electrode (first electrode), PZT piezoelectric ceramics and a Pt electrode (second electrode) on the SOI wafer in sequence to prepare the PZT-SOI wafer. The thicknesses of the first electrode and the second electrode are both 150 nm; the thickness of the PZT piezoelectric ceramic was 2 μm.
S20, as shown in (b) of FIG. 5, coating photoresist 5 μm on the upper surface with the upper electrode, prebaking for 90S, exposing for 45S, developing for 50S, rinsing with deionized water for 30S, drying with nitrogen gas, postbaking for 12min, and wet etching PZT 90S. Then immersing PZT into prepared etching liquid for etching, and stirring the etching liquid by using a magnetic stirrer to improve the etching uniformity and speed; wherein, the stirring speed is 130r/min during PZT etching, and the stirring temperature is normal temperature during PZT etching; then putting the etched PZT-SOI into the prepared HNO3Soaking in the solution for 3 min; finally, the mixture is put into deionized water to be soaked for a few minutes so as to clean and remove surface impurities. Drying by nitrogen and vacuum drying. And exposing a square first bonding pad of the lower electrode on the upper surface of the device after etching, wherein the length and the width of the first bonding pad are both 260 mu m.
As a preferable mode, the PZT is immersed in the prepared etching solution for etching, and the adopted etching solution is prepared by the following method: first 1.50gNH4F, slowly adding the mixture into 2ml of deionized water, and continuously stirring until the mixture is completely dissolved; then 1ml of NH4F (40%) is slowly poured into 4ml of HF solution, and is continuously stirred to be uniformly mixed to form BHF solution; then 1ml BHF, 26ml HCl and 186ml H2Preparing etching mixed liquid, and fully stirring to fully and uniformly mix the etching mixed liquid to obtain etching liquid; and then immersing PZT into the prepared etching liquid for etching, and stirring the etching liquid by using a magnetic stirrer to improve the etching uniformity and speed.
Preferably, the desired HNO is3The solution was prepared as follows: adding 7ml of HNO3Put 20ml of H2And O forms a solution and is stirred uniformly.
S30, as shown in (c) of FIG. 5, coating 5 μm photoresist protection on the front surface (upper surface) of the PZT-SOI wafer, coating 20 μm photoresist on the back surface, prebaking for 2min, developing for 130S, rinsing with deionized water for 30S, drying with nitrogen, postbaking for 12min, and etching with NMC medium for 1.5 μm SiO2(ii) a Etching to obtain the SiO with the spiral shape of the imitated cochlea2And (6) a graph. And the cochlear helical SiO2The width of the graph is gradually wider from the center to the outer edge along the spiral line, and is 0.25mm larger than the cochlear implant spiral upper electrode, so that the back cavity can cover the whole front cochlear implant spiral vibrating membrane. Cochlear spiral-shaped SiO2The spiral number of turns of the figure is 3 turns of the real cochlea.
S40, as shown in FIG. 5 (d), then deep silicon etching Si to SiO with NMC2Stop barrier layer of SiO2The barrier layer is arranged between the lower electrode and the back cavity and is used as an actuating layer to form a back cavity with a cochlear-like spiral cavity structure, and the preparation of the back cavity is completed.
The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes or modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention.
Claims (10)
1. A piezoelectric MEMS speaker of a cochlear-like spiral diaphragm structure, comprising:
the back cavity is arranged at the bottom of the substrate, and a cavity of the back cavity is in a cochlear-like spiral shape;
a first electrode disposed on the upper surface of the substrate and on the upper surface of the backside cavity, the first electrode being spaced apart from the cavity of the backside cavity by an actuation layer for generating vibrations;
a piezoelectric layer disposed on an upper surface of the first electrode;
the second electrode is arranged on the piezoelectric layer, and the second electrode and the piezoelectric layer are in a cochlear-imitated spiral shape;
the actuating layer, the first electrode, the piezoelectric layer and the second electrode form a cochlear-like spiral vibrating membrane, and the cochlear-like spiral vibrating membrane corresponds to the back cavity up and down in position and is matched in shape.
2. The cochlear implant spiral diaphragm structure-imitating piezoelectric MEMS speaker according to claim 1, wherein an outer contour of the back cavity overlies an outer contour of the cochlear implant spiral diaphragm.
3. The cochlear implant spiral diaphragm structure piezoelectric MEMS speaker of claim 1, wherein the cochlear implant spiral diaphragm is wider from the center along the spiral line to the outer edge.
4. The cochlear implant diaphragm structure piezoelectric MEMS speaker of claim 3, wherein the cochlear implant spiral shaped cavity of the back cavity is wider from the center along a spiral line to the outer edge, and the width of the back cavity is greater than the width of the cochlear implant spiral shaped diaphragm.
5. The cochlear implant spiral diaphragm structure-imitating piezoelectric MEMS speaker according to claim 1, wherein the first electrode is provided with a first pad, and the first pad is exposed to an upper surface of the device; the second electrode is provided with a second pad.
6. The cochlear implant spiral diaphragm structure-imitating piezoelectric MEMS speaker according to any one of claims 1 to 5, wherein the substrate is an SOI wafer, a flexible material substrate, a metal substrate or a non-metal substrate.
7. The piezoelectric MEMS speaker with cochlear implant-like spiral diaphragm structure as claimed in any one of claims 1 to 5, wherein the material of the first electrode and the second electrode is selected from any one of platinum, gold, chromium or aluminum.
8. The piezoelectric MEMS speaker with cochlear implant-like spiral diaphragm structure as claimed in any one of claims 1 to 5, wherein the piezoelectric layer is made of any one of PZT piezoelectric ceramic, zinc oxide, aluminum nitride, lead magnesium niobate-lead titanate or polyvinylidene fluoride.
9. The cochlear implant spiral diaphragm structure piezoelectric MEMS speaker of any one of claims 1 to 5, wherein the number of turns of the spiral of the cochlear implant spiral diaphragm and the back cavity matches the number of turns of the real cochlea.
10. A method for manufacturing a cochlear-like spiral diaphragm structure piezoelectric MEMS speaker as claimed in any one of claims 1 to 9, comprising:
preparing a first electrode on a substrate;
preparing a piezoelectric layer on the first electrode;
preparing a second electrode on the piezoelectric layer;
etching the second electrode to obtain a cochlear-like spiral second electrode pattern and a second electrode pad;
wet etching is carried out on the piezoelectric layer, a cochlear spiral-shaped piezoelectric layer pattern is etched, and the first electrode pad are exposed;
and etching the back of the substrate to form a cochlear-like spiral back cavity, wherein the part of the substrate, which is not etched, between the cavity of the back cavity and the first electrode is an actuating layer.
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